TopLine announces a new Graphite Tool (patent pending) for precision positioning of 0.4 mm diameter micro-coil springs onto BGA1738 organic substrates as an alternative to conventional solder balls. Micro-coil springs, originally introduced by NASA, provide compliant interconnects between IC packages and the Printed Circuit Board (PCB). The footprint of 1738 packages is 42.5 mm x 42.5 mm with a pad pitch of 1.0mm. After attaching micro-coil springs, the reworked package provides more compliancy than BGA (Ball Grid Array) solder balls to absorb stress caused by CTE mismatch, and to increase solder joint reliability under harsh operating conditions.
The company’s Graphite tool securely locks organic or ceramic LGA substrates in place while micro-coil springs are attached to the substrate. The procedure is simple: an operator places the LGA inside of the tool. Next, a layer of solder paste is printed on the LGA pads using a 125 um thick stainless-steel stencil. Afterwards, the springs are dropped in place using the company’s Flip-Pack cassette. After depositing the springs into the graphite, the operator removes the cassette. The next step is to place the graphite into a vapor-phase reflow oven to form solder fillets that permanently secures the micro-coil spring to the IC substrate. After cool-down, the CGA is gently removed using an engineered extraction tool.